The grid system of the streets allows for plenty of sunlight plus there are plenty of smaller buildings between the taller skyscrapers. I was tanned from walking around Manhattan after four days, last June.

From 1916 to the 1950s, the zoning laws resulted in wedding cake buildings which started at the sidewalk line at ground level and had setbacks at various heights to let sunlight reach the street. From the 1950s, architects designed buildings like the UN that went straight up but were set in the middle of plazas with open space around them. Short buildings can be replaced by taller buildings to a maximum specified size. If the owners of the short buildings don't intend to take advantage of that right, they can sell the right to an adjoining owner who can make his proposed new building bigger with the air rights transferred from the neighbor.

As the buildings grew taller in the early 20th Century, the lack of sunshine on the street level indeed became an issue. One of the worst examples of tall buildings blocking the Sun is the Equitable Insurance Company Building in the Lower Manhattan, built in 1915. The 1.2 million square foot, 40-story building sits on a plot of less than one acre.

Opponents were outraged by the building which cast a permanent shadow on three nearby buildings lower than 21 floors and on the Singer Building up to 27th floor and the City Investing Building up to 24th floor. Many people could foresee that construction of similar buildings would lead to the City to become a maze of dark streets. This led to the City adopting a 1916 Zoning Resolution which limited the height and required setbacks to allow the sunlight to penetrate to the street level.

There are indeed some areas, that receive next to little or NO sunlight, because of the concentration and height of nearby buildings.

Trump once wanted to build the tallest skyscraper in the world, (at that time) and his plan was shot down, because such a monstrosity, would have cast a shadow over much of central park, for most of the day.

For streets that have tall buildings on both sides, such as in the east 50s and around Wall Street, there are only a few hours a day when you can directly see the sun from the street. At other hours, the sun is blocked by buildings. Individuals who work in such buildings generally know, based on the season, which hours they will have directly sunlight and when they won't.

That's the origin of the expression "canyons of New York"--a narrow street with tall structures on each side.